Breast cancer is the most common malignancy in women. For cancer diagnosis, the search for concealed metastases is the single most important factor in the treatment decision for all cancer patients. Even though current methods such as NMR have improved the detection of metastasis, the majority of metastases are rarely detected early. Contrast agents are being developed to selectively highlight cancerous tissue as compared with normal tissue. The most active approach is with the use of antibody-based contrast agents. These agents are costly and have limitations secondary to immunogenicity, purity and manufacturability. This grant application proposes the development of a non-protein based contrast agent for use in MR imaging which would selectively highlight primary and metastatic breast cancer tumors. This new tumor specific technology would be superior to other approaches in that the agent is non- immunogenic, pure, easily manufactured, and low cost. The aim of Phase I is to synthesize, purify, characterize and perform MR imaging studies with a model MR contrast agent that is specific for breast cancer. Phase II proposes making analogs of this compound, evaluating these analogs using in vitro and in vivo models, and performing pre-clinical studies on the optimal compound. Clinical evaluation of the optimal compound is scheduled for SBIR Phase III.